2nd quarter Science

• Electromagnetic waves are transverse waves, meaning that the oscillations of the electric and magnetic fields are perpendicular to the direction of wave propagation.
• Wavelength refers to the distance from one peak to another on an EM wave.
• Maxwell - Contributed to developing equations showing the relationship of electricity magnetism
• Hertz - Showed experimental evidence of electromagnetic waves and their link to light.
• Ampere - Demonstrated the magnetic effect based on the direction of current
• Faraday - Formulated the principle behind electromagnetic induction
• Oersted - Showed how a current carrying wire behaves like a magnet.
• Transverse Waves - Oscillations are up and down or from side to side.
• Longitudinal Waves - The oscillation are in the direction of travel
• Longitudinal Waves - particles of the medium move parallel to the propagation of the wave
• Transverse Wave - particles in the medium move perpendicular to the direction of propagation of the wave
• Characteristics of Longitudinal:

  
  

  • medium moves in the same direction of the wave
  • acts in 1 dimension
  • wave cannot be polarized
  • can be produced in any medium such as gas, liquid, or solid
  • P-wave
  • rarefaction and compression
• Characteristics of Transverse Wave

  • moving perpendicular to the direction of the wave
  • acts in 2 dimension
  • can be polarized
  • can be produced in solid and liquid's surface
  • S-wave
  • troughs and crests
• Electromagnetic Waves - waves that are created as a result of vibrations between an electric field and a magnetic field.
• Characteristic of EM Waves:

  • do not need medium to travel
  • composed of electric and magnetic fields
  • can travel through a vacuum
  • range of all types of EM Radiation
• Radiation - The term used to describe the transfer of energy in the form of EM wave.
• Characteristics of Mechanical Wave:

  • need medium to travel
  • composed of vibration
  • cannot travel through a vacuum
• Waves - A disturbance that travels or propagates from the place where it was created.
• Radio Wave

  • wavelength range from a few millimeters (tenths of inches) to hundreds of kilometers (hundreds of miles). 
  • oscillate at frequencies between a few kilohertz (kHz or thousands of hertz) and a few terahertz (THz or 1012 hertz).
  • extensively for communications.
• Microwave

  • short wavelength radio waves which we use for cooking and for communication. 
  • have wavelengths between a few millimeters and tens of centimeters (tenths of inches to tens of inches).
• Infrared - borders radio waves along the electromagnetic spectrum and has slightly higher energy and shorter wavelengths than radio waves.
• Visible Light - Makes up just a portion of the entire electromagnetic spectrum, from 380-700 nanometers.
• Ultraviolet Radiation

  • Purple and violet light have shorter wavelengths than other colors of light, and ultraviolet has even shorter waves than violet does; so ultraviolet is sort of "purpler-than-purple" light or "beyond violet" light.
• a static distribution of charges produces an electric field
• charges in motion (an electrical current) produce a magnetic field
• a changing magnetic field produces an electric field, moving charges
• • Electric and Magnetic fields produce forces on charges
• An accelerating charge produces electromagnetic waves (radiation)
• Both electric and magnetic fields can transport energy
• All electromagnetic radiation travels at c =  3×10^8 m/s in vacuum
• Generation of Radio waves

  • charge
  • oscillation
  • polarization
• • Receiving antenna works best when ‘tuned’ to the wavelength of the signal, and has proper polarization
  • Electrons in antenna are “jiggled”

  by passage of electromagnetic wave
• AM - uses changes in the signal strength to convey information
• AM - uses frequency range from 530 kHz to 1700 kHz
• AM - uses frequency range from 530 kHz to 1700 kHz
• AM - spacing is 10 kHz (a little breathing room) → 117 channels
• AM - 9 kHz of bandwidth means 4.5 kHz is highest audio frequency that can be encoded
• typical speech sound of 500 Hz varies 1000 times slower than carrier
• FM - uses changes in the wave’s frequency to convey information
• FM - spans 87.8 MHz to 108.0 MHz in 200 kHz intervals; 101 possible stations